1. Field of the Invention
This invention relates to a method of and an apparatus for inspecting an end portion of an object for a defect.
2. Description of the Prior Art
A method of inspecting a lip of a glass for a defect is conventionally known and disclosed, for example, in JP-A-1-129112. According to the method disclosed, light is projected to the opposite inner and outer portions of a lip of an object, and reflected light from the inner and outer portions of the lip is received by a single one-dimensional image sensor. When an output of the image sensor is taken out, if the lip is normal, then the output presents two pulses corresponding to reflected light from the inner and outer portions of the lip. The distance between the two pulses varies in accordance with a thickness of the lip while the widths of the pulses vary in accordance with a height of the lip but by small amounts. Thus, according to the method, the distance between the two pulses is compared with a reference value to detect an abnormal thickness of the lip, and the widths of the pulses are compared with a reference value to detect an abnormal height of the lip. Besides, the fact that the lip has some uneven or convex and concave profile is detected from absence of either of such pulses.
According to the conventional method, a satisfactory result of inspection is obtained for a defect caused by deformation of the lip in a horizontal direction since a pulse varies in response to a variation of the lip in the horizontal direction by an amount which increases in proportion to such variation of the lip. However, since the width of a pulse varies in response to a variation of the lip in a vertical direction but by a small amount, a satisfactory result of inspection cannot be obtained for a defect caused by deformation of the lip in the vertical direction. Although it is possible to detect, using the conventional method, a significantly uneven, convex and concave profile of a lip because a pulse is absent, it is very difficult to detect a defect such as a down sealing surface or a waving surface of a lip of an object which presents a continuously and moderately deformed profile in a vertical direction.